1. Field of the Invention
The present invention relates to a semiconductor device encapsulant, consisting of an epoxy resin composition, for providing a cured product having a high thermal shock resistance and high humidity resistance.
2. Description of the Related Art
Conventionally, an epoxy resin composition containing a phenol novolak resin as a curing agent has been used as a semiconductor device encapsulant. This resin composition has been mainly used since its cured product has excellent humidity resistance, high-temperature electrical characteristics and molding properties, and the like.
Recently, as semiconductor elements have been more integrated, functional units on an element have been more miniatualized and a size of a pellet itself have been rapidly increased. Due to such changes in a pellet, a conventional epoxy resin composition has become unable to satisfy characteristics such as a thermal shock resistance. That is, if a conventional epoxy resin composition is used to encapsulate a large pellet having a fine surface structure, a phospho-silicate glass (PSG) film or silicon nitride (Si.sub.3 N.sub.4) film as a passivation film of an aluminum (Al) pattern formed on the surface of the pellet may crack, or the encapsulating resin may crack. This tendency is significantly increased especially when a thermal cycle test is performed. As a result, an outer appearance of a package or reliability of a semiconductor device is degraded.
In addition, when a surface-mounting type package is to be soldered, the entire package is exposed to a high-temperature atmosphere at 200.degree. to 260.degree. C. for 5 to 90 seconds, i.e., subjected to a severe thermal shock. In this case, cracks may be produced in the encapsulating resin mainly due to vaporization of water absorbed inside it.
In order to solve the above problems, a stress applied on an insert by the encapsulating resin must be reduced, and the encapsulating resin itself must be strengthened throughout a wide temperature range.
In order to reduce an internal stress of the encapsulating resin, it is considered effective to form a so-called sea-island structure in which silicone oil or natural rubber is finely dispersed in a resin matrix. Actually, an internal stress of the encapsulating resin can be considerably reduced by this technique. This technique, however, inevitably has a problem of reducing the strength of a resin cured product and has almost no effect on preventing cracks on a cured product at high temperatures.